A new three-dimensional supramolecular [Ce2（2,5-pydc）3（H2O）2]（1） has been hydrothermally synthesized at 180 ℃ and characterized by single-crystal X-ray diffraction.X-ray crystal analyses reveal that the compoun...A new three-dimensional supramolecular [Ce2（2,5-pydc）3（H2O）2]（1） has been hydrothermally synthesized at 180 ℃ and characterized by single-crystal X-ray diffraction.X-ray crystal analyses reveal that the compound belongs to the monoclinic system,space group P21/c,C21H13Ce2N3O14,a = 6.561（1）,b = 17.986（5）,c = 9.411（3） ,β = 95.558（5）° and Z = 2.In the structure of 1,each Ce（1） center is surrounded by 2,5-pydc ligands,forming the 6-connected node,and the 2,5-pydc ligand coordinates to the Ce（Ⅲ） in two different coordination modes.In mode 1,the four oxygen atoms of two carboxyl groups connect neighboring Ce（Ⅲ） ions,giving 4-connected（4-c） second building unit（SBU-1）.Furthermore,the structure is extended into a 2-D layer from SBU-1 by sharing Ce（1） atoms.In mode 2,the ligand coordinates to the Ce（Ⅲ） ion from the adjacent chain with the 4-connected（4-c） second building unit（SBU-2）,generating a 1-D ladder from SBU-2 by sharing Ce（1） atoms.Finally,the structure is extended into a 6,4,4-c network.Its photoluminescence property was also investigated.展开更多
The distribution of C<sub>4</sub> plants and the C<sub>4</sub>/C<sub>3</sub> ratio along Northeast China transect （NECT） have been studied. A model to quantify their relation with...The distribution of C<sub>4</sub> plants and the C<sub>4</sub>/C<sub>3</sub> ratio along Northeast China transect （NECT） have been studied. A model to quantify their relation with environmental factors has been set up. The ratio of the number of C<sub>4</sub> plants to that of C<sub>3</sub> plants along NECT shows two low and two high trends from east to west, and their distribution is mainly decided by annual average temperature and precipitation.展开更多
To improve the performance of LiFePO4, single phase Li1-4xTixFePO4/C (x=0, 0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of...To improve the performance of LiFePO4, single phase Li1-4xTixFePO4/C (x=0, 0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy observations(SEM), charge/discharge test, carbon analysis and electrochemical impedance spectroscopy(EIS). The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti^(4+) does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti^(4+) (molar fraction) has good electrochemical performance delivering about an initial specific capacity of 146.7 mA·h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti^(4+).展开更多
文摘A new three-dimensional supramolecular [Ce2（2,5-pydc）3（H2O）2]（1） has been hydrothermally synthesized at 180 ℃ and characterized by single-crystal X-ray diffraction.X-ray crystal analyses reveal that the compound belongs to the monoclinic system,space group P21/c,C21H13Ce2N3O14,a = 6.561（1）,b = 17.986（5）,c = 9.411（3） ,β = 95.558（5）° and Z = 2.In the structure of 1,each Ce（1） center is surrounded by 2,5-pydc ligands,forming the 6-connected node,and the 2,5-pydc ligand coordinates to the Ce（Ⅲ） in two different coordination modes.In mode 1,the four oxygen atoms of two carboxyl groups connect neighboring Ce（Ⅲ） ions,giving 4-connected（4-c） second building unit（SBU-1）.Furthermore,the structure is extended into a 2-D layer from SBU-1 by sharing Ce（1） atoms.In mode 2,the ligand coordinates to the Ce（Ⅲ） ion from the adjacent chain with the 4-connected（4-c） second building unit（SBU-2）,generating a 1-D ladder from SBU-2 by sharing Ce（1） atoms.Finally,the structure is extended into a 6,4,4-c network.Its photoluminescence property was also investigated.
文摘The distribution of C<sub>4</sub> plants and the C<sub>4</sub>/C<sub>3</sub> ratio along Northeast China transect （NECT） have been studied. A model to quantify their relation with environmental factors has been set up. The ratio of the number of C<sub>4</sub> plants to that of C<sub>3</sub> plants along NECT shows two low and two high trends from east to west, and their distribution is mainly decided by annual average temperature and precipitation.
基金Project(04JJ0388) supported by the National Science Foundation of Hunan Province, China
文摘To improve the performance of LiFePO4, single phase Li1-4xTixFePO4/C (x=0, 0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy observations(SEM), charge/discharge test, carbon analysis and electrochemical impedance spectroscopy(EIS). The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti^(4+) does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti^(4+) (molar fraction) has good electrochemical performance delivering about an initial specific capacity of 146.7 mA·h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti^(4+).
